1. Field of the Invention
The invention relates to a manufacturing method for a circuit board, and particularly relates to a manufacturing method for a multi-layer circuit board.
2. Description of Related Art
As the integration of electronic products is increasingly improved, a circuit layer of a circuit board applied to the high-integration electronic products increases from single layer, double layer to 6 layers, 8 layers and even more than 10 layers, so as to mount more electronic components on a printed circuit board. Generally speaking, the most common manufacturing process for a circuit board is the lamination process. When the lamination process is used to manufacture the circuit board, an alignment accuracy between each circuit layer and insulating layer needs to be appropriately controlled. Therefore, in the manufacturing process of the circuit board, a plurality of alignment targets are usually formed in a previous stacking layer through a photolithography process. Then, after another layer is added, X ray is used to find the alignment targets of the previous layer, and a milling process is performed to form alignment targets for a subsequent process.
However, since the alignment targets in the previous stacking layer are formed through the photolithography process, the process itself already causes errors. When the milling process using X ray is performed, additional errors in the milling process also occur. Thus, alignment errors caused by the alignment targets of each layer continuously accumulate. If a number of circuit layers of the circuit board increases, the accumulated errors of the alignment targets also increase, resulting in an overly large deviation of an interlayer alignment accuracy that makes a design of conductive holes and bonding pads on bottom layers unable to be miniaturized.